fix(kbsearch): rank FTS correctly, filter before -n, start the daemon. (#5)

Go search took worst BM25 hits (ORDER BY score), cut to -n before --root,
and never called ensureDaemon. Ranking and flag parsing move to a cgo-free
package so CI can fail those regressions without ladybug. --hop errors
instead of being swallowed into the query.

bin/kbsearch/rank/query.go

@@ -0,0 +1,9 @@
+package rank
+
+// BM25 ranks best-first, so the top hits are the *highest* scores; cosine
+// distance ranks best-first ascending. Both mirror kblib.py.
+const FTSStmt = "CALL QUERY_FTS_INDEX('Leaf', 'id', $q) " +
+	"RETURN node.id, node.text, node.root, node.source, score ORDER BY score DESC LIMIT $n"
+
+const VecStmt = "CALL QUERY_VECTOR_INDEX('Leaf', 'Leaf_vec', $q, $n) " +
+	"RETURN node.id, node.text, node.root, node.source, distance ORDER BY distance LIMIT $n"